CA1322284C - Molded camshaft assembly - Google Patents
Molded camshaft assemblyInfo
- Publication number
- CA1322284C CA1322284C CA000592532A CA592532A CA1322284C CA 1322284 C CA1322284 C CA 1322284C CA 000592532 A CA000592532 A CA 000592532A CA 592532 A CA592532 A CA 592532A CA 1322284 C CA1322284 C CA 1322284C
- Authority
- CA
- Canada
- Prior art keywords
- camshaft
- cam
- camshaft assembly
- assembly
- plastics material
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C3/00—Shafts; Axles; Cranks; Eccentrics
- F16C3/02—Shafts; Axles
- F16C3/026—Shafts made of fibre reinforced resin
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/44—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C37/00—Component parts, details, accessories or auxiliary operations, not covered by group B29C33/00 or B29C35/00
- B29C37/0003—Discharging moulded articles from the mould
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
- B29C45/14598—Coating tubular articles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/26—Moulds
- B29C45/33—Moulds having transversely, e.g. radially, movable mould parts
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/02—Valve drive
- F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
- F01L1/047—Camshafts
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2077/00—Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2031/00—Other particular articles
- B29L2031/748—Machines or parts thereof not otherwise provided for
- B29L2031/7484—Cams
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2031/00—Other particular articles
- B29L2031/748—Machines or parts thereof not otherwise provided for
- B29L2031/75—Shafts
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C2360/00—Engines or pumps
- F16C2360/18—Camshafts
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49229—Prime mover or fluid pump making
- Y10T29/49293—Camshaft making
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T74/00—Machine element or mechanism
- Y10T74/21—Elements
- Y10T74/2101—Cams
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Ocean & Marine Engineering (AREA)
- Valve-Gear Or Valve Arrangements (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
Abstract of the Disclosure A camshaft assembly for an internal combus-tion engine includes a rotatable camshaft and a cam lobe mounted on the camshaft for rotation therewith.
The cam lobe includes first and second axial ends and an integral crowned cam profile formed in its periphery which includes a radially extending shoulder located between the first and second ends. The shoulder may be formed by a pair of axially extending parallel tapered surfaces in the cam profile. A method of molding the camshaft assembly is also disclosed.
The cam lobe includes first and second axial ends and an integral crowned cam profile formed in its periphery which includes a radially extending shoulder located between the first and second ends. The shoulder may be formed by a pair of axially extending parallel tapered surfaces in the cam profile. A method of molding the camshaft assembly is also disclosed.
Description
:~ 32228~ ~
MOLDED CAMSHAFT ASSEMBLY
Background of the Invention The present invention relates to camshaft assemblies, and more particularly to a molded camshaft assembly for an internal combustion engine.
Small internal combustion engines, such as those used on lawn mowers and snow blowers, generally include a cam gear and at least one cam lobe mounted on a camshaft. The camshaft is rotated by means of the cam gear, which, as is conventional, meshes with a timing gear on a crankshaft to rotate in timed relation to the engine cycle. The cam lobe is used to control an exhaust and an intake valve, as is also convention-al.
In the past, such cam lokes have been formed of metallic materials utilizing time consuming and expensive precision machining methods. For example, metallic ca~ lobes are generally made by utilizing a hobbing machine to cut the cam lobe from a solid piece of metal. Hobbing cam lobes may also result in undesirable high waste or scrap material which further increases their cost of manufac~ure.
More recently, it has been found that non-metallic cam lobes may be molded from plastics material with sufficient accuracy for small internal combustion engines. Such molded non-metallic cam lobes provide for reduced noise and lower cost compared with metallic cam lobes.
When the camshaft rotates in timed relation to the engine cycle, the cam lobe rotates therewith and acts through cam followers that are positioned to ride on the peripheral surface or profile of the cam lobe and are operatively connected with valves that are cyclically opened when the engine is running to control the intake and exhaust systems of an internal com~us-tion engine. If the follower rides on the edge of thecam lobe, excessive stress and pitting of the peripheral surface of the cam profile may occur.
~rowning of the cam profile generally helps to solve this problem. Crowning provides a profile such that the highest point of the cam lobe's peripheral surface which contacts the cam follower is at or near the center of the lobe. In order to crown the cam profile utilizing a conventional molding process, the die tooling typically becomes more expensive and complex with the result that only two cavities may be utilized with such mold compared with four cavities with simpler tooling. More specifically, if the cam mold tooling may be pulled off axially, the tooling is less expensive and complex and four cavities may used in the mold. Normally, however, if axially movable tooling would be utilized to mold a cam lobe, the cam profile cannot be crowned since crowning would normally require the mold tooling to be pulled off radially at 90~ to the camshaft axis. As a result, conventional molding techniques would require that a cam lobe have an axially tapered cam profile to allow the tooling to be pulled off axially. Unfortunately, with an axially tapered cam profile the follower would ride on the high edge of the cam profile causing excessive wear and pitting, as noted above.
It is therefore desirable to provide a cam lobe which may be molded of non-metallic materials using a relatively inexpensive molding process which would provide a cam profile that avoids or eliminates excessive wear.
Summary of the Invention A camshaft assembly for an internal combus-tion engine.
.
"` ~3222~
- 2a 1 The in~ention p~o~ides a method of molding an internal combustion en~ine camshaft assembly including a camshaft and an integral cam lobe and with said lobe having a crowned cam profile with an apex~ comprising the steps of:
~a) providing a mold including a die component axially closeable to define a mold cavity having first surface portions in the shape of a camshaft which defines an axis o~ rotation and having second sur~ace portions shaped to define the cam lobe of the assembly, said second surface portions including a radially outer surface delineating the crowned cam profile and apex of the cam lobe, said apex of said radially outer surface being disposed radially outwardly of a lower edge of a portion of said die component; (b~ filling said mold cavity with a shrinkable fluid plastics material so that said material forms a camshaft assembly conforming to the shape of and initially engaging said first and second surface portions of said mold cavity; (c) delaying for a predetermined period of time so that said plastics material hardens and shrinks radially inwardly away from said radially outer mold cavity surface until the apex portion of the camshaft assembly cam profile is finally disposed radially inwardly of said lower edge of said die component portion; (d~ and then opening said mold by moving said die component only in an axial direction so that said lower edge of said die component portion passes freely over said apex portion of the camshaft assembly cam profile.
B
~ ~222~ ~
In one aspect, the invention comprises a method of moldin~ a camshaft assembly which includes a camshaft and integral cam lobe for an internal combus-tion engine. The steps include providing a mold including a die component cl~sable to define a mold cavity having a ~irst portion in the shape of a camshaft which defines an axis of rotation and a second portion in the shape of a cam lobe which includes a crowned cam profile, filling the mold cavity with a shrinkable fluid plastics material, waiting a predeter~
mined period of time to permit the plastics material in the second portion of the mold cavity to harden and shrink, and moving the die component in an axially direction to open the mold. The fluid plastics material has a shrinkage rate of at least about 0.000067 inches per second, and preferably comprises a heated molten plastics material such as unreinforced or reinforced nylon. When utilizing a heated molten plastics material with suitable shrinkage characteristics such as nylon, the step of waiting includes cooling the molten material for a period of time between 0 and 30 seconds, preferably less than 5 seconds. Also, the filling step preferably is accomplished via injection molding techniques.
In another as~ect of the invention, the camshaft assembly includes a camshaft defining an axis of rotation, and a stepped cam lobe mounted on the camshaft for rotation therewith having first and second axial ends. The stepped cam lobe has an integral cam profile for~ed in its peripheral surface which includes a shoulder located between the first and second ends of the cam lobe which has a radial dimension ecual to or greater than the radial dimension of the first and second ends.
-:"' ; ' - ' .' ~: .
1 3 2 2 2 8 ~ r The stepped cam profile includes first and second axially extending tapered sur~ces wi~h the ~irst tapered surface extending axially from the first end to the shoulder, and the second tapered surface extending axially rom ~he shoulder to the second end of the cam lobe. Additionally, the first and second tapered surfaces of the cam profile generally extend parallel to one another. The stepped profile causes a tappet follower to contact the cam profile away from the edge of the cam so that the cam follower rides away from the cam surface edge to reduce wear and to enable the cam lobe to be produced by a relativley inexpensive molding technique.
In a modified form of the stepped profile, the step in the central region of the profile is molded with exterior and interior radii to smooth the transition.
In yet another aspect of the invention, the camshaft assembly comprises a metal camshaft together with an all-plastic cam assembly mounted on the camshaft for rotation t~erewith. Such a camshaft assembly is referred to herein as a "composite"
assembly. The all-plastic cam assembly includes a cam gear, an exhaust cam lobe and an intake cam lobe, each of which is a~ially spaced apart from one another and integra]ly interconnected by a hollow sleeve member which surrounds the metal camshaft. Additionally, in still another aspect of the invention, the entire camshaft assembly including both the cam assembly and the cainshaft is composed of a plastics material and formed integrally with the journal bearing ends of the sleeve member. Thus, an all-plastic camshaft assembly is provided wherein the intake cam lobe t the exhaust cam lobe, the cam gear and the camshaft are each 3~ composed of a plastics material and integrally formed together as a one-piece assembly.
:L322284 Benefits of making the camshaft assembly in either the composite ~orm or entirely of non-metallic or plascics material include:
l. ~uiet operation, due to resilient, damped gear tooth and bearing non-~ietallic material used.
MOLDED CAMSHAFT ASSEMBLY
Background of the Invention The present invention relates to camshaft assemblies, and more particularly to a molded camshaft assembly for an internal combustion engine.
Small internal combustion engines, such as those used on lawn mowers and snow blowers, generally include a cam gear and at least one cam lobe mounted on a camshaft. The camshaft is rotated by means of the cam gear, which, as is conventional, meshes with a timing gear on a crankshaft to rotate in timed relation to the engine cycle. The cam lobe is used to control an exhaust and an intake valve, as is also convention-al.
In the past, such cam lokes have been formed of metallic materials utilizing time consuming and expensive precision machining methods. For example, metallic ca~ lobes are generally made by utilizing a hobbing machine to cut the cam lobe from a solid piece of metal. Hobbing cam lobes may also result in undesirable high waste or scrap material which further increases their cost of manufac~ure.
More recently, it has been found that non-metallic cam lobes may be molded from plastics material with sufficient accuracy for small internal combustion engines. Such molded non-metallic cam lobes provide for reduced noise and lower cost compared with metallic cam lobes.
When the camshaft rotates in timed relation to the engine cycle, the cam lobe rotates therewith and acts through cam followers that are positioned to ride on the peripheral surface or profile of the cam lobe and are operatively connected with valves that are cyclically opened when the engine is running to control the intake and exhaust systems of an internal com~us-tion engine. If the follower rides on the edge of thecam lobe, excessive stress and pitting of the peripheral surface of the cam profile may occur.
~rowning of the cam profile generally helps to solve this problem. Crowning provides a profile such that the highest point of the cam lobe's peripheral surface which contacts the cam follower is at or near the center of the lobe. In order to crown the cam profile utilizing a conventional molding process, the die tooling typically becomes more expensive and complex with the result that only two cavities may be utilized with such mold compared with four cavities with simpler tooling. More specifically, if the cam mold tooling may be pulled off axially, the tooling is less expensive and complex and four cavities may used in the mold. Normally, however, if axially movable tooling would be utilized to mold a cam lobe, the cam profile cannot be crowned since crowning would normally require the mold tooling to be pulled off radially at 90~ to the camshaft axis. As a result, conventional molding techniques would require that a cam lobe have an axially tapered cam profile to allow the tooling to be pulled off axially. Unfortunately, with an axially tapered cam profile the follower would ride on the high edge of the cam profile causing excessive wear and pitting, as noted above.
It is therefore desirable to provide a cam lobe which may be molded of non-metallic materials using a relatively inexpensive molding process which would provide a cam profile that avoids or eliminates excessive wear.
Summary of the Invention A camshaft assembly for an internal combus-tion engine.
.
"` ~3222~
- 2a 1 The in~ention p~o~ides a method of molding an internal combustion en~ine camshaft assembly including a camshaft and an integral cam lobe and with said lobe having a crowned cam profile with an apex~ comprising the steps of:
~a) providing a mold including a die component axially closeable to define a mold cavity having first surface portions in the shape of a camshaft which defines an axis o~ rotation and having second sur~ace portions shaped to define the cam lobe of the assembly, said second surface portions including a radially outer surface delineating the crowned cam profile and apex of the cam lobe, said apex of said radially outer surface being disposed radially outwardly of a lower edge of a portion of said die component; (b~ filling said mold cavity with a shrinkable fluid plastics material so that said material forms a camshaft assembly conforming to the shape of and initially engaging said first and second surface portions of said mold cavity; (c) delaying for a predetermined period of time so that said plastics material hardens and shrinks radially inwardly away from said radially outer mold cavity surface until the apex portion of the camshaft assembly cam profile is finally disposed radially inwardly of said lower edge of said die component portion; (d~ and then opening said mold by moving said die component only in an axial direction so that said lower edge of said die component portion passes freely over said apex portion of the camshaft assembly cam profile.
B
~ ~222~ ~
In one aspect, the invention comprises a method of moldin~ a camshaft assembly which includes a camshaft and integral cam lobe for an internal combus-tion engine. The steps include providing a mold including a die component cl~sable to define a mold cavity having a ~irst portion in the shape of a camshaft which defines an axis of rotation and a second portion in the shape of a cam lobe which includes a crowned cam profile, filling the mold cavity with a shrinkable fluid plastics material, waiting a predeter~
mined period of time to permit the plastics material in the second portion of the mold cavity to harden and shrink, and moving the die component in an axially direction to open the mold. The fluid plastics material has a shrinkage rate of at least about 0.000067 inches per second, and preferably comprises a heated molten plastics material such as unreinforced or reinforced nylon. When utilizing a heated molten plastics material with suitable shrinkage characteristics such as nylon, the step of waiting includes cooling the molten material for a period of time between 0 and 30 seconds, preferably less than 5 seconds. Also, the filling step preferably is accomplished via injection molding techniques.
In another as~ect of the invention, the camshaft assembly includes a camshaft defining an axis of rotation, and a stepped cam lobe mounted on the camshaft for rotation therewith having first and second axial ends. The stepped cam lobe has an integral cam profile for~ed in its peripheral surface which includes a shoulder located between the first and second ends of the cam lobe which has a radial dimension ecual to or greater than the radial dimension of the first and second ends.
-:"' ; ' - ' .' ~: .
1 3 2 2 2 8 ~ r The stepped cam profile includes first and second axially extending tapered sur~ces wi~h the ~irst tapered surface extending axially from the first end to the shoulder, and the second tapered surface extending axially rom ~he shoulder to the second end of the cam lobe. Additionally, the first and second tapered surfaces of the cam profile generally extend parallel to one another. The stepped profile causes a tappet follower to contact the cam profile away from the edge of the cam so that the cam follower rides away from the cam surface edge to reduce wear and to enable the cam lobe to be produced by a relativley inexpensive molding technique.
In a modified form of the stepped profile, the step in the central region of the profile is molded with exterior and interior radii to smooth the transition.
In yet another aspect of the invention, the camshaft assembly comprises a metal camshaft together with an all-plastic cam assembly mounted on the camshaft for rotation t~erewith. Such a camshaft assembly is referred to herein as a "composite"
assembly. The all-plastic cam assembly includes a cam gear, an exhaust cam lobe and an intake cam lobe, each of which is a~ially spaced apart from one another and integra]ly interconnected by a hollow sleeve member which surrounds the metal camshaft. Additionally, in still another aspect of the invention, the entire camshaft assembly including both the cam assembly and the cainshaft is composed of a plastics material and formed integrally with the journal bearing ends of the sleeve member. Thus, an all-plastic camshaft assembly is provided wherein the intake cam lobe t the exhaust cam lobe, the cam gear and the camshaft are each 3~ composed of a plastics material and integrally formed together as a one-piece assembly.
:L322284 Benefits of making the camshaft assembly in either the composite ~orm or entirely of non-metallic or plascics material include:
l. ~uiet operation, due to resilient, damped gear tooth and bearing non-~ietallic material used.
2. Quiet operati~n~ due to low inertia and light weiyht oE non-metallic material used.
3. Quiet oper~tion, due to smooth surface finish achievable in molding of non-metallic material.
4. Desirable smooth surface finish is achievable as molded; thus expensive grinding is not needed on cam lobes and bearing journals as would be required with metal camshaft assemblies.
5. The levels of geometric accuracy and precision normally required for metal cam gear teeth and camshaft assembly bearings are not required for camshaft assemblies made of plastics or non-metallic materials, because noise is not as sensitive to accuracy and precision when non-metallics are used. For example, small nicks or gouges on gear tee~h or cam lobes will heal during normal operation, and will not cause excessive noise.
6. Bearings need not be as accurate because resilient materials will facilitate small deforma-tions which w~ll facilitate load sharing and -elastohydrodynamic action, allowing the bearings to carry unusually high bearing loads without excessive wear.
7. Camshaft assembl_es made of plastics or non-metalic materials are less sensitive to stresses because the relatively resilient material will deform slightly and spread the loads of mating gear teeth and valve tappets.
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8. To minimize stress and to promote low vibration and noise, it is desirable to utilize polynomial cam lobe profiles, and to crown the lobes, If the lobes are crowned, the cam followers run at or near to the lobe axial centers, and the force application points will not move back ~nd forth on the lobes.
Though normally these geometric shapes are expensive to achieve when using metals since ~xpensive grinding is normally required, these shapes can be molded into the camshaft assembly at no extra cost using plastics or non-metallic materials.
Crowning the lobes also has a beneficial ef~ect to compensate for "sinking", which causes undesirable depressions in the middle of the lobes, caused by shrinkage during cooling. The material in the center oE the lobes cools last, resulting in depressions unless the lobes are crowned, 9. To minimize gear tooth stress which promotes long life, it is desirable that a full root radius be used. Though normally this would rquire expensive unusual tooling to be used with metallic materials, it can be molded at no significant extra cost into a part made of plastics or non-metallic material.
Though normally these geometric shapes are expensive to achieve when using metals since ~xpensive grinding is normally required, these shapes can be molded into the camshaft assembly at no extra cost using plastics or non-metallic materials.
Crowning the lobes also has a beneficial ef~ect to compensate for "sinking", which causes undesirable depressions in the middle of the lobes, caused by shrinkage during cooling. The material in the center oE the lobes cools last, resulting in depressions unless the lobes are crowned, 9. To minimize gear tooth stress which promotes long life, it is desirable that a full root radius be used. Though normally this would rquire expensive unusual tooling to be used with metallic materials, it can be molded at no significant extra cost into a part made of plastics or non-metallic material.
10. Conical, or tapered gear teeth are desirable to promote low noise due to improved tooth load pick-up and improved lubrication.
Though normally with metallic gears this shape would be dirficult to obtain, it can be easily achieved with molded plastics or non-metalllc cam gear assemblies.
Though normally with metallic gears this shape would be dirficult to obtain, it can be easily achieved with molded plastics or non-metalllc cam gear assemblies.
11. Compression-release function desired for easy engine starting can be achieved with camshaft I
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132~28~ ~
assemblies made of plastic at no extra co~t by ~olding small bumps into the intake or exhaust cam lobe profiles. In contrast, this would normally require extra effort to grind these shapes into the cam lohe profiles of a metallic camshaft assembly.
. . . .
132~28~ ~
assemblies made of plastic at no extra co~t by ~olding small bumps into the intake or exhaust cam lobe profiles. In contrast, this would normally require extra effort to grind these shapes into the cam lohe profiles of a metallic camshaft assembly.
12. Significant ~oise and noise quality improvements can be achieved using plastics or non-metallics in camshaft assemblies, because the contacts with mating parts of gear teeth, journal bearings, thrust bearings and cam lobes are made with resilient, damped material.
13. Use o plastics or non-metallic materials promotes improved life of mating parts of the engine because the plastics or non-metallic material has a low-friction, non-abrasive rubbing action if any contact is made.
14. Camshaft assemblies made of plastics or non-metallic materials can be design-optimized for use on relatively low-speed engines (less than 5,000 rpm and preferably less than about 4,000 rpm) used for lawn-mowing applicat-ons. Metallic camshaft assemblies tend to be over desi~ned and ~-relatively expensi~e for this application.
15. Camshaft assemblies made of plastics or non-metallic materials can be design-optimized for use on relatively short (b;ut adequate) life engines (1,000 to 3,000 hours) used for lawn-mowing applications. Metallic camshaft assemblies tend to be over designed and relatively expensive for this application.
16. Gear diameter is usually a highly critical dimension when metal gears are used, because of noise, stress, wear and life ~nSi~erations. When plastics or non-metallics materia]s are used for the cam gear the successful ..... ~ . :
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operation is not as sensitive to this dimension.
Noise, stress, wear and life appear to still be adequate, in spite of high or low back lash, or even gear tooth interference. In addition to diameter, the gears do not have to be as round as they have to be when metal gears are ~sed.
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operation is not as sensitive to this dimension.
Noise, stress, wear and life appear to still be adequate, in spite of high or low back lash, or even gear tooth interference. In addition to diameter, the gears do not have to be as round as they have to be when metal gears are ~sed.
17. When plastics or non-metallic materials are used for gear teeth, and loading occurs, as in a power take-off or auxiliary drive application, the teeth can bend slightly, sharing the load, minimizing wear, extending life and minimizing noise.
18. Low-cost tooling can be used to take advantage of the inherent shrinkage of the polymer resins.
19. Camshaft assemblies made entirely of plastics or non-metallic materials and with adequate life and quality can be manufactured at much lower cost than with metals.
The non-metallic materials that would be considered for the making of engine camshaft assemblies might include various grades of thermoplastic resins such as: nylon (castable and/or injection moldable grades), phenolics, liquid crystal polymers, and poly-amide-imide. In addition, various polymer blends might be considered. Various fillers, powders, reinforcement fibers, and solid lubricants might also be considered.
Brief Description of the Drawings The drawings illustrate the best mode presently contemplated of carrying out the invention.
In the drawings:
Fig. l is a side view in elevation of a composite camshaft assembly including a stepped cam lobe in accordance with the present invention;
132~284 g Fi~. 2 is a fraymentary end view of the camshaft assembly of Fig~ 1 taken along the plane of the line 2-2 in Fig. l;
Fig. 3 i5 a fragmer.tary enlarged side view in elevation of the stepped cam profile for the cam lobe of Fig. l;
Fig. ~ is a fragmentary enlarged side view in elevation of a modified stepped cam profile for the cam lobe of Fig. l;
Fig. 5 is a fragmentary enlarged cross sectional view showing the die components of a mold in their closed position for making the camshaft assembly of the present invention which illustrates a third embodiment of a cam lobe having an arcuate cam profile;
Fig. 6 is a fragmentary cross sectional view of an all-plastic camshaft assembly;
Fig. 7 is a fragmentary cross sectional view similar to Fig. 6 of a second embodiment of a composite camshaft assembly utilizing a tubular metal support ~
insert; and ~ -Fig. 8 ls a fragmentary cross sectional view similar to Fi~s. 6 and 7 of a third embodiment of a composite camshaft utilizing a solid metal support insert.
Description of the Preferred Embodiment Referring now to the drawings, Fig. 1 illustrates a camshaft assembly, generally designated by the numeral 1, constituting a preferred embodiment of the present invention. The camshaft assembly 1 shown in Fig. 1 is specifically adapted for use in a small internal combustio~ engine of the type generally utilized with lawn mowers and snow blowers. However, as is readily obvious to those skilled in the art, the camshaft assembly 1 of the present invention may be adapted for use with other types of internal combuskion engines as well as other types of apparatus.
~. . ..
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1 3 2 2 2 8 d~L r Camshaft assembly l includes a cam gear 2, an intake cam lobe 3 and an exhaust cam lobe 4 mounted on a camshaft 5 of an internal combustion engine. The camshaft 5 is rotated about an axis oE rotation 6 in timed relation to the engine cycle by means cf cam gear l, as is conventional, which meshes with a timing gear (not shown) on the engine crankshaft. Camshaft 5 includes journals 16, 17 at opposite ends thereof for supporting camshaft assembly l in bearings (not shown) in the engine housing, as is conventional. Cam lobe 3 is used to control an intake valve (not shown) while cam lobe 4 is used to control an exhaust valve tnot shown), as is also conventional.
In the embodiment illustrated in Fig. l, cam gear 2 and cam lobes 3 and 4 are integrally molded together of a plastics material, such as reinforced or unreinforced nylon, as a one-piece assembly and are interconnected by means of a hollow sleeve 7 to form an integral all-plastic cam assembly. Camshaft 5, in turn, consists of a unitary solid membeL composed of a metallic material, and is of circular cross section about which the integral cam assembly consisting of cam gear 2, cam lobes 3 and 4 and sleeve 7 are fixedly mounted. This camshaft assembly is referred to herein as a "composite" camshaft assembly.
Referring now to ~ig. 7, there is il1ustrated a second embodiment of a composite camshaft assembly, In this second embodiment, camshaft 5a consists of a unitary tub~lar member composed of a metallic material, and is of circular cross section about which the integral cam assembly consisting of the cam gear, cam lobes (only intake cam lobe 3a being shown~ and sleeve 7a are fixedly mounted. Note that the ends of camshaft 5a are covered by plastics materlal to form the journals (only journal 16a being shown). Thus, - \
~32228~
carnshaft 5a functlons merely as a stiffenin~ or support insert in this embodiment.
Fig. 8 illustrates a third embodiment of a composite camshaft assembly, and shows an intake cam lobe 3b, sleeve 7b and journal 16b of an inteqral plastics cam assembly fixedly mounted on a camshaft 5b. This third embodiment is thus similar to the second embodiment of Fig. 7 except camshaft Sb is a unitary solid metallic member of circular cross section. Additionally, and similar to the second embodiment, camshaft 5b functions merely as a stiffening or support insert.
It should be noted, however, that camshaft 5 may also be composed of a plastics material such as reinforced or unrein~orce~ nylon, as well as other plastics materials, if desired. Under such circumstances, camshaft 5 would not consist of a separate metallic member as shown in Figs. 1, 7 and 8 extending through sleeve 7 and the entire integral cam assembly. Instead, hollow sleeve 7 would essentially become the camshaft with journals 16, 17 also comprising hollow members integrally attached to opposite ends of sleeve 7 to form an integral one-piece "all-plastic" camshaft assembly. This ail-plastic camshaft assembly is illustrated in Fig. 6 showing an intake cam lobe 3c, sleeve 7c and journal 16c.
The non-metallic materials that would be considered for the making of either the co~posite or al1-plastic engine camshaft assemblies might include various grades of thermoplastic resins such as: nylon (castable and/or injection moldable grades), phenolics, liquid crystal polymers, and poly-amide-imide. In additon, various polymer blends might be considered.
Various fillers, powders, reinforcement fibers, and solid lubricants might also be considered.
, ~ ~
Castable nylon performs quite well, but the processing appears to be relatively expensive.
Phenolic material C05t iS relatively low, but processing involves relatively high cost because of relatively long mold cycle times. The phenolic material can be molded very accurately, but it is very hard and brittle. To improve toughness, it preferably is reinforced with glass or other fiber, or fiberglass cloth. These reinforcing materials, however, may increase cost and/or cause abrasive wear of mating parts. Liquid crystal polymers ~LCP'S) would perform well in the engine. ~lowever, they are fairly new, and material cost appears to be relatively high. Poly-amide-imide material (trade name "Torlon") appears to have excellent high temperature strength, but it appears to be somewhat hard and brittle, and cost also appears to be relatively high. Injection moldable nylon performs well, and costs of material and processing are relatively low. Stresses appear to be at or beyond recommènded limits at engine operating temperatures, but the ~am life still appears to be adequate. Injection molded nylon appears to be the best choice for small engines without "over-design", and high shrinkage in the mold makes possible the use of lo~-cost tooling.
As shown best in Fig. 2, cam lobes 3 and 4 include profiles 8 and 9, respectively, about their o~ter peripheral surfaces upon which the tappet follower (not shown) of the respective intake and exhaust valves ride for controlling the flow of gases between intake and exhaust ports communicating with the engine combustion chamber. As shown, the projecting portions of cam lobes 3, 4 are offset with respect to one another about 90 so as to cyclically open its respective valve during engine operation, as is conven-tional.
L3222~4 ~ r ~
~ 1 3--Referring now to Fig. 3, there is illustrated in detail cam profile 8. As shown, cam profile 8 is "stepped" and includes a shoulder 10 formed in the peripheral surface of cam profile 8 between opposite axial ends 11, 12 of cam lobe 3. Shoulder 10 is defined by a first axially extending tapered surface 13 and a second axially extending tapered surface 14 which extends parallel to tapered surface 13. As shown, tapered surface 13 extends axially from end 11 of cam lobe 3 to the upper edge of shoulder 10 such that the upper edge of shoulder 10 extends a radial distance outwardly of end 11. Tapered surface 14 extends axially fro~ shoulder 10 to the opposite end 12 of cam lobe 3. Tapered surface 14 extends from the lower edge or radially inner edge of shoulder 10 to the edge of end 12 such that the edge of end 12 is located at a radial distance equal to or less than the radial extent of the upper edge of shoulder 10, as shown best by the horizontal line 15 in Fig. 3. As sho~7n best in Fig. 1, shoulder 10 extends around the entire profile 8 of cam lobe 3.
Referring to Fig. 4, there is illustrated an alternate form of cam profile 8. The stepped profile 8 of Fig. 4 is similar to that illustrated in Fig. 3 and 2~ therefore like numerals except with the subscript "a"
are utili7ed for like elements. However, step or shoulder 10 of profile 8 in Fig. 3 is replaced by a transition shoulder or step 32 including external radius 33 and internal radius 34.
Referring now to Fig. 5, there is illustrated a fragmentary view showing a portion of the mold for making camshaft assembly 1. More specifically, Fig. 5 illustrates a cam lobe 18 integrally molded together with a hollow sleeve 19 in a manner similar to that shown in Fig. 1, except that profile 20 of cam lobe 18 "
:
~32228~ ~
is "arcuate" in shape instead of being "stepped" in shape. As illustrated, the apex of profile 20 has a radial dimension equal to or greater than the radial dimension of either of opposite axial ends 21, 22 of cam lobe 18. This arcuate shape of the peripher~l surface of cam profile 20 extends around the entire profile 20 of cam lobe 18.
It should be noted that both the stepped cam profile 8 (see Figs. 3 and 4) as well as the arcuate profile 20 ~see Fig. 5) may be defined as illustrating "crowned" cam lobes. Thus, the term "crowned cam profile" includes both the stepped profiles of Figs. 3 and 4 as well as the arcuate profile of Fig. S so long as the high point of the profile has a radial dimension equal to or greater than the radial dimension of either of the opposite ends of the cam lobe.
Referring once again to Fig. 5, the mold shown therein includes an axially movable die component 23, and a radially movable die component 24 which form a mold cavity having a first portion 25 in the shape of sleeve 19 and a second portion 26 in the shape of cam lobe 18 which, as illu~trated, in_ludes a "crowned" cam profile, i.e. in this case arcuate shaped. Thus, the second portion 26 of the mold cavity has an arcuate shaped surface 27 corresponding to profile 20 of cam lobe 18.
As illustrated, die component 23 is movable axially in the direction illustrated by arrow 28, and die component 24 is movable radially as illustrated by the arrow 29. However, under normal molding circumstances/ die component 23 may not be moved axially since portion 30 thereof would not clear the apex of cam profile 20 after molding, as is clearly evident from the fact that portion 30 e~tends radially inwardly of the apex of profile 20. Therefore, in . ~ .
' , ' '' ."'' '' . . . ' ' . ' 132228~ ~
orde~ to permit die component 23 to be pulled of f .
axially, the present invention includes a method of molding camshaft assembly 1 such that the mold cavity is filled with a shrinkable fluid plastics material, and thereafter waiting a predetermined period of time to permit the plastics material in cam lobe por~ion 26 of the mold cavity to simultaneously solidify and shrink so that the apex of profile 20 of cam lobe 18 after shrinking is radially inwardly of the lower edge of portion 30 of die component 23, a.s indicated by the dotted line 31 in Fig. 4. In order to accomplish this, the fluid plastics material m~st have a shrinkage rate of at least abou~ 0.000067 inches per second. If the material does not have such a shrinkage rate, the cycle time for manufacturing such camshaft assemblies becomes excessively long and as a result more expensi~, Such materials are typically heated molten plastics material injected into the mold cavity. Typical of such plastics material is a nylon based material such as reinforced or unreinforced nylon or a blend of nylon with other plastics materials so long as the blend has the above shrinkage rate characteristic. The waiting time enables the molten material to cool for a period of time between O and 30 seconds, pref erably less than 5 seconds, so that the material shrinks su~f iciently to enable die component 23 to be moved axially to open the mold cavity. As is apparent, the mold cavity must be initially over dimensioned so that upon shrinkage the proper radial dimension of cam lobe 18 is obtained.
In order to demonstrate the advantages of making the camshaft assembly or the cam gear assembly entirely of non-metallic or plastics material to form either a composite or an all-plastic camshaft assembly, numerous sound tests were performed and various noise data was collected. Table I illustrates a competitive ~ 3222~ ~
engine evaluatlon which includes various small engines typically utillzed for lawn and garden type applications.
Table I
Competitive Engine Noise Evaluation 4 Meter Energy Average (dB) Engine Make, r1odel3200 RP~3000 RPM27C0 RPM
Engine #1, 1 73.8 72.5 70.9 Briggs & Stratton Max-40 73.5 72.5 71.0 Engine #2, 1 72.1 71.6 71.2 Engine #3, 1 OHV 72.1 71.1 69.9 Engine #3, 2 2-Stroke71.6 70.9 69.7 Briggs & Stratton Quantum 70.7 69.7 67.5 Engine ~4, 1 OHV 69.5 68.5 67.5 Engine #4, 2 OHV
Mower w/o Blade 70.4 ---- 58.7 Engine #4/ 3 OHV
Mower w/o Blade ---- ---- 67.0 In the above Table I, the Briggs & Stratton Quantum engine has incorporated therein a composite camshaft assembly comprising a metallic camshaft, and an integrally molded cam gear, cam lobes and thrust bearings composed of a nylon material. Table I
demonstrates that the Briggs ~ Stratton Quantum engine is significantly quieter with an average decibel reading of 69.3 at 4 meters over an operating range of 2700 to 3200 revolutions per minute.
Table II demonstrates nolse data obtained from two different model 92~ Briggs & Stratton engines utiliæing a composite camsh3ft assembly similar to that utilized to obtain the data in Table I. The model 929 engine included a muffler, intake silencer, and its drive shaft was loaded with only an inertia disk. The noise data was taken at a 4 meter distance over a range of 2700, 3000 and 3300 revolutions per minute.
~l 3 2~ 2 2 8 4 Table TI
Composite Camshaft Noise Tests Briggs ~ Stratton Model 929 Engine Muffler, Intake Silencer, Inertia Disk Load 4r~ . Energy_Averaqe (dB) l. Engine #1, with73.1 71.6 70.2 Std. Metal Assembly 2. Engine ~l, with70.5 68.6 66.7 Composite Assembly 3. Engine #2, with72.5 71.4 70.6 Std. Metal Assembly 4. Engine $2, with69.6 68.2 67 Composite Assembly As can be seen from the above data in Table II, the camshaft assembly of the present invention significantly reduces the noise emanating Erom an englne .
The following Table III was another test performed to obtain noise data on a model 94908 Briggs & Stratton engine including an air vane governcr thereon. The tests were per~ormed with different types of camshaft assemblies with the pinion on the crankshaft which drove the cam gear having various mounting arrangements. The noise data was obtained at 4 meters over a range of 2400 to 3200 revolutions per minute.
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The above data from Table III once again illustrates that a camshaft assembly in accordance with the present invention substantially reduces the noise as compared to standard as well as other types of camshaft assemblies.
Referring now to Table IV, there is shown a further noise comparison between the camshaft assembly of the present invention incorporated in a model 8 Briggs & Stratton quiet engine and a standard model 8 Briggs & Stratton quiet engine. The standard model 8 engine utilized a conventional metallic camshaft assembly. Both engines were fitted with an infinite muffler and an intake silencer. The noise data was taken at a 1 meter distance and the tests were r~n under full load and no load drive shaft conditions at both 3000 and 3600 rpms.
Table IV
Noise Comparison 20Composite Camshaft vs. Standard Camshaft Briggs & Stratton Model 8 Quiet ~ngines Infinite Muffler - Intake Silencer lM. Energy Average (dB) Full No Full No Test Load Load Load Load l. Standard Quiet Model 8 82.6 81.4 (Average of 4) 79-4 77-4 2. Composite Camshaft 80.1 77.4 TR #10062 75 72.8 Once again, the data shown in Table IV
illustrates a substantial reduction in noise when the composite camshaft of the present invention is incorporated in a standard model 8 Briggs & Stratton engine.
~3222~ ~
Finally, additional noise tests were run on a model 60102 Briggs & Stratton engine in order to test six different composite camshaft assemblies made from production tooling. Table V summarizes the noise data obtained therefrom. The model 60102 engine included an infinite muffler and intake silencer and the readings were taken at 1 meter with no load on the engine drive shaft. In this test, the primary concern was with no load mechanical noise, and therefore the tests were run with an infinite muffler and intake silencer. All the no load test results are summarized in Table V.
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~322284 As shown from the above data, there was almost a 3 decibel average noise reduction at 3600 rpms. The improvements increase with lowered engine speed until an average of about 5.6 decibels of noise reduction was obtained at 2400 rpm. One camshaft assembly, namely 2-Cl, did not perform as well as the others. The 2-Cl camshaft assembly was 1.5 decibel higher than the average of the other 5 camshaft assemblies at 3600 rpm. A later or second retest confirmed the higher noise levels. The character of the noise appeared to indicate some type of valve impact noise, and a careful check of the cams revealed a fairly large deviation of the exhaust cam profile for 2-Cl. This deviation would change the valve velocity and acceleration and could cause excessive noise from valve seat impact or lifter impact. However, even with all of the faults of the 2-Cl, the 2-Cl still tested 1.7 decibels quieter at 3600 rpm than the standard metal assembly.
The present invention thus provides a camshaft assembly for engine use which has numerous advantages with ~uiet operation and low manufacturing costs being two of the most desirable advantages.
Various modes of carrying out the invention are contemplated as being within the scope of the fvllowing claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.
B
.. . .
The non-metallic materials that would be considered for the making of engine camshaft assemblies might include various grades of thermoplastic resins such as: nylon (castable and/or injection moldable grades), phenolics, liquid crystal polymers, and poly-amide-imide. In addition, various polymer blends might be considered. Various fillers, powders, reinforcement fibers, and solid lubricants might also be considered.
Brief Description of the Drawings The drawings illustrate the best mode presently contemplated of carrying out the invention.
In the drawings:
Fig. l is a side view in elevation of a composite camshaft assembly including a stepped cam lobe in accordance with the present invention;
132~284 g Fi~. 2 is a fraymentary end view of the camshaft assembly of Fig~ 1 taken along the plane of the line 2-2 in Fig. l;
Fig. 3 i5 a fragmer.tary enlarged side view in elevation of the stepped cam profile for the cam lobe of Fig. l;
Fig. ~ is a fragmentary enlarged side view in elevation of a modified stepped cam profile for the cam lobe of Fig. l;
Fig. 5 is a fragmentary enlarged cross sectional view showing the die components of a mold in their closed position for making the camshaft assembly of the present invention which illustrates a third embodiment of a cam lobe having an arcuate cam profile;
Fig. 6 is a fragmentary cross sectional view of an all-plastic camshaft assembly;
Fig. 7 is a fragmentary cross sectional view similar to Fig. 6 of a second embodiment of a composite camshaft assembly utilizing a tubular metal support ~
insert; and ~ -Fig. 8 ls a fragmentary cross sectional view similar to Fi~s. 6 and 7 of a third embodiment of a composite camshaft utilizing a solid metal support insert.
Description of the Preferred Embodiment Referring now to the drawings, Fig. 1 illustrates a camshaft assembly, generally designated by the numeral 1, constituting a preferred embodiment of the present invention. The camshaft assembly 1 shown in Fig. 1 is specifically adapted for use in a small internal combustio~ engine of the type generally utilized with lawn mowers and snow blowers. However, as is readily obvious to those skilled in the art, the camshaft assembly 1 of the present invention may be adapted for use with other types of internal combuskion engines as well as other types of apparatus.
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. .
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1 3 2 2 2 8 d~L r Camshaft assembly l includes a cam gear 2, an intake cam lobe 3 and an exhaust cam lobe 4 mounted on a camshaft 5 of an internal combustion engine. The camshaft 5 is rotated about an axis oE rotation 6 in timed relation to the engine cycle by means cf cam gear l, as is conventional, which meshes with a timing gear (not shown) on the engine crankshaft. Camshaft 5 includes journals 16, 17 at opposite ends thereof for supporting camshaft assembly l in bearings (not shown) in the engine housing, as is conventional. Cam lobe 3 is used to control an intake valve (not shown) while cam lobe 4 is used to control an exhaust valve tnot shown), as is also conventional.
In the embodiment illustrated in Fig. l, cam gear 2 and cam lobes 3 and 4 are integrally molded together of a plastics material, such as reinforced or unreinforced nylon, as a one-piece assembly and are interconnected by means of a hollow sleeve 7 to form an integral all-plastic cam assembly. Camshaft 5, in turn, consists of a unitary solid membeL composed of a metallic material, and is of circular cross section about which the integral cam assembly consisting of cam gear 2, cam lobes 3 and 4 and sleeve 7 are fixedly mounted. This camshaft assembly is referred to herein as a "composite" camshaft assembly.
Referring now to ~ig. 7, there is il1ustrated a second embodiment of a composite camshaft assembly, In this second embodiment, camshaft 5a consists of a unitary tub~lar member composed of a metallic material, and is of circular cross section about which the integral cam assembly consisting of the cam gear, cam lobes (only intake cam lobe 3a being shown~ and sleeve 7a are fixedly mounted. Note that the ends of camshaft 5a are covered by plastics materlal to form the journals (only journal 16a being shown). Thus, - \
~32228~
carnshaft 5a functlons merely as a stiffenin~ or support insert in this embodiment.
Fig. 8 illustrates a third embodiment of a composite camshaft assembly, and shows an intake cam lobe 3b, sleeve 7b and journal 16b of an inteqral plastics cam assembly fixedly mounted on a camshaft 5b. This third embodiment is thus similar to the second embodiment of Fig. 7 except camshaft Sb is a unitary solid metallic member of circular cross section. Additionally, and similar to the second embodiment, camshaft 5b functions merely as a stiffening or support insert.
It should be noted, however, that camshaft 5 may also be composed of a plastics material such as reinforced or unrein~orce~ nylon, as well as other plastics materials, if desired. Under such circumstances, camshaft 5 would not consist of a separate metallic member as shown in Figs. 1, 7 and 8 extending through sleeve 7 and the entire integral cam assembly. Instead, hollow sleeve 7 would essentially become the camshaft with journals 16, 17 also comprising hollow members integrally attached to opposite ends of sleeve 7 to form an integral one-piece "all-plastic" camshaft assembly. This ail-plastic camshaft assembly is illustrated in Fig. 6 showing an intake cam lobe 3c, sleeve 7c and journal 16c.
The non-metallic materials that would be considered for the making of either the co~posite or al1-plastic engine camshaft assemblies might include various grades of thermoplastic resins such as: nylon (castable and/or injection moldable grades), phenolics, liquid crystal polymers, and poly-amide-imide. In additon, various polymer blends might be considered.
Various fillers, powders, reinforcement fibers, and solid lubricants might also be considered.
, ~ ~
Castable nylon performs quite well, but the processing appears to be relatively expensive.
Phenolic material C05t iS relatively low, but processing involves relatively high cost because of relatively long mold cycle times. The phenolic material can be molded very accurately, but it is very hard and brittle. To improve toughness, it preferably is reinforced with glass or other fiber, or fiberglass cloth. These reinforcing materials, however, may increase cost and/or cause abrasive wear of mating parts. Liquid crystal polymers ~LCP'S) would perform well in the engine. ~lowever, they are fairly new, and material cost appears to be relatively high. Poly-amide-imide material (trade name "Torlon") appears to have excellent high temperature strength, but it appears to be somewhat hard and brittle, and cost also appears to be relatively high. Injection moldable nylon performs well, and costs of material and processing are relatively low. Stresses appear to be at or beyond recommènded limits at engine operating temperatures, but the ~am life still appears to be adequate. Injection molded nylon appears to be the best choice for small engines without "over-design", and high shrinkage in the mold makes possible the use of lo~-cost tooling.
As shown best in Fig. 2, cam lobes 3 and 4 include profiles 8 and 9, respectively, about their o~ter peripheral surfaces upon which the tappet follower (not shown) of the respective intake and exhaust valves ride for controlling the flow of gases between intake and exhaust ports communicating with the engine combustion chamber. As shown, the projecting portions of cam lobes 3, 4 are offset with respect to one another about 90 so as to cyclically open its respective valve during engine operation, as is conven-tional.
L3222~4 ~ r ~
~ 1 3--Referring now to Fig. 3, there is illustrated in detail cam profile 8. As shown, cam profile 8 is "stepped" and includes a shoulder 10 formed in the peripheral surface of cam profile 8 between opposite axial ends 11, 12 of cam lobe 3. Shoulder 10 is defined by a first axially extending tapered surface 13 and a second axially extending tapered surface 14 which extends parallel to tapered surface 13. As shown, tapered surface 13 extends axially from end 11 of cam lobe 3 to the upper edge of shoulder 10 such that the upper edge of shoulder 10 extends a radial distance outwardly of end 11. Tapered surface 14 extends axially fro~ shoulder 10 to the opposite end 12 of cam lobe 3. Tapered surface 14 extends from the lower edge or radially inner edge of shoulder 10 to the edge of end 12 such that the edge of end 12 is located at a radial distance equal to or less than the radial extent of the upper edge of shoulder 10, as shown best by the horizontal line 15 in Fig. 3. As sho~7n best in Fig. 1, shoulder 10 extends around the entire profile 8 of cam lobe 3.
Referring to Fig. 4, there is illustrated an alternate form of cam profile 8. The stepped profile 8 of Fig. 4 is similar to that illustrated in Fig. 3 and 2~ therefore like numerals except with the subscript "a"
are utili7ed for like elements. However, step or shoulder 10 of profile 8 in Fig. 3 is replaced by a transition shoulder or step 32 including external radius 33 and internal radius 34.
Referring now to Fig. 5, there is illustrated a fragmentary view showing a portion of the mold for making camshaft assembly 1. More specifically, Fig. 5 illustrates a cam lobe 18 integrally molded together with a hollow sleeve 19 in a manner similar to that shown in Fig. 1, except that profile 20 of cam lobe 18 "
:
~32228~ ~
is "arcuate" in shape instead of being "stepped" in shape. As illustrated, the apex of profile 20 has a radial dimension equal to or greater than the radial dimension of either of opposite axial ends 21, 22 of cam lobe 18. This arcuate shape of the peripher~l surface of cam profile 20 extends around the entire profile 20 of cam lobe 18.
It should be noted that both the stepped cam profile 8 (see Figs. 3 and 4) as well as the arcuate profile 20 ~see Fig. 5) may be defined as illustrating "crowned" cam lobes. Thus, the term "crowned cam profile" includes both the stepped profiles of Figs. 3 and 4 as well as the arcuate profile of Fig. S so long as the high point of the profile has a radial dimension equal to or greater than the radial dimension of either of the opposite ends of the cam lobe.
Referring once again to Fig. 5, the mold shown therein includes an axially movable die component 23, and a radially movable die component 24 which form a mold cavity having a first portion 25 in the shape of sleeve 19 and a second portion 26 in the shape of cam lobe 18 which, as illu~trated, in_ludes a "crowned" cam profile, i.e. in this case arcuate shaped. Thus, the second portion 26 of the mold cavity has an arcuate shaped surface 27 corresponding to profile 20 of cam lobe 18.
As illustrated, die component 23 is movable axially in the direction illustrated by arrow 28, and die component 24 is movable radially as illustrated by the arrow 29. However, under normal molding circumstances/ die component 23 may not be moved axially since portion 30 thereof would not clear the apex of cam profile 20 after molding, as is clearly evident from the fact that portion 30 e~tends radially inwardly of the apex of profile 20. Therefore, in . ~ .
' , ' '' ."'' '' . . . ' ' . ' 132228~ ~
orde~ to permit die component 23 to be pulled of f .
axially, the present invention includes a method of molding camshaft assembly 1 such that the mold cavity is filled with a shrinkable fluid plastics material, and thereafter waiting a predetermined period of time to permit the plastics material in cam lobe por~ion 26 of the mold cavity to simultaneously solidify and shrink so that the apex of profile 20 of cam lobe 18 after shrinking is radially inwardly of the lower edge of portion 30 of die component 23, a.s indicated by the dotted line 31 in Fig. 4. In order to accomplish this, the fluid plastics material m~st have a shrinkage rate of at least abou~ 0.000067 inches per second. If the material does not have such a shrinkage rate, the cycle time for manufacturing such camshaft assemblies becomes excessively long and as a result more expensi~, Such materials are typically heated molten plastics material injected into the mold cavity. Typical of such plastics material is a nylon based material such as reinforced or unreinforced nylon or a blend of nylon with other plastics materials so long as the blend has the above shrinkage rate characteristic. The waiting time enables the molten material to cool for a period of time between O and 30 seconds, pref erably less than 5 seconds, so that the material shrinks su~f iciently to enable die component 23 to be moved axially to open the mold cavity. As is apparent, the mold cavity must be initially over dimensioned so that upon shrinkage the proper radial dimension of cam lobe 18 is obtained.
In order to demonstrate the advantages of making the camshaft assembly or the cam gear assembly entirely of non-metallic or plastics material to form either a composite or an all-plastic camshaft assembly, numerous sound tests were performed and various noise data was collected. Table I illustrates a competitive ~ 3222~ ~
engine evaluatlon which includes various small engines typically utillzed for lawn and garden type applications.
Table I
Competitive Engine Noise Evaluation 4 Meter Energy Average (dB) Engine Make, r1odel3200 RP~3000 RPM27C0 RPM
Engine #1, 1 73.8 72.5 70.9 Briggs & Stratton Max-40 73.5 72.5 71.0 Engine #2, 1 72.1 71.6 71.2 Engine #3, 1 OHV 72.1 71.1 69.9 Engine #3, 2 2-Stroke71.6 70.9 69.7 Briggs & Stratton Quantum 70.7 69.7 67.5 Engine ~4, 1 OHV 69.5 68.5 67.5 Engine #4, 2 OHV
Mower w/o Blade 70.4 ---- 58.7 Engine #4/ 3 OHV
Mower w/o Blade ---- ---- 67.0 In the above Table I, the Briggs & Stratton Quantum engine has incorporated therein a composite camshaft assembly comprising a metallic camshaft, and an integrally molded cam gear, cam lobes and thrust bearings composed of a nylon material. Table I
demonstrates that the Briggs ~ Stratton Quantum engine is significantly quieter with an average decibel reading of 69.3 at 4 meters over an operating range of 2700 to 3200 revolutions per minute.
Table II demonstrates nolse data obtained from two different model 92~ Briggs & Stratton engines utiliæing a composite camsh3ft assembly similar to that utilized to obtain the data in Table I. The model 929 engine included a muffler, intake silencer, and its drive shaft was loaded with only an inertia disk. The noise data was taken at a 4 meter distance over a range of 2700, 3000 and 3300 revolutions per minute.
~l 3 2~ 2 2 8 4 Table TI
Composite Camshaft Noise Tests Briggs ~ Stratton Model 929 Engine Muffler, Intake Silencer, Inertia Disk Load 4r~ . Energy_Averaqe (dB) l. Engine #1, with73.1 71.6 70.2 Std. Metal Assembly 2. Engine ~l, with70.5 68.6 66.7 Composite Assembly 3. Engine #2, with72.5 71.4 70.6 Std. Metal Assembly 4. Engine $2, with69.6 68.2 67 Composite Assembly As can be seen from the above data in Table II, the camshaft assembly of the present invention significantly reduces the noise emanating Erom an englne .
The following Table III was another test performed to obtain noise data on a model 94908 Briggs & Stratton engine including an air vane governcr thereon. The tests were per~ormed with different types of camshaft assemblies with the pinion on the crankshaft which drove the cam gear having various mounting arrangements. The noise data was obtained at 4 meters over a range of 2400 to 3200 revolutions per minute.
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The above data from Table III once again illustrates that a camshaft assembly in accordance with the present invention substantially reduces the noise as compared to standard as well as other types of camshaft assemblies.
Referring now to Table IV, there is shown a further noise comparison between the camshaft assembly of the present invention incorporated in a model 8 Briggs & Stratton quiet engine and a standard model 8 Briggs & Stratton quiet engine. The standard model 8 engine utilized a conventional metallic camshaft assembly. Both engines were fitted with an infinite muffler and an intake silencer. The noise data was taken at a 1 meter distance and the tests were r~n under full load and no load drive shaft conditions at both 3000 and 3600 rpms.
Table IV
Noise Comparison 20Composite Camshaft vs. Standard Camshaft Briggs & Stratton Model 8 Quiet ~ngines Infinite Muffler - Intake Silencer lM. Energy Average (dB) Full No Full No Test Load Load Load Load l. Standard Quiet Model 8 82.6 81.4 (Average of 4) 79-4 77-4 2. Composite Camshaft 80.1 77.4 TR #10062 75 72.8 Once again, the data shown in Table IV
illustrates a substantial reduction in noise when the composite camshaft of the present invention is incorporated in a standard model 8 Briggs & Stratton engine.
~3222~ ~
Finally, additional noise tests were run on a model 60102 Briggs & Stratton engine in order to test six different composite camshaft assemblies made from production tooling. Table V summarizes the noise data obtained therefrom. The model 60102 engine included an infinite muffler and intake silencer and the readings were taken at 1 meter with no load on the engine drive shaft. In this test, the primary concern was with no load mechanical noise, and therefore the tests were run with an infinite muffler and intake silencer. All the no load test results are summarized in Table V.
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~322284 As shown from the above data, there was almost a 3 decibel average noise reduction at 3600 rpms. The improvements increase with lowered engine speed until an average of about 5.6 decibels of noise reduction was obtained at 2400 rpm. One camshaft assembly, namely 2-Cl, did not perform as well as the others. The 2-Cl camshaft assembly was 1.5 decibel higher than the average of the other 5 camshaft assemblies at 3600 rpm. A later or second retest confirmed the higher noise levels. The character of the noise appeared to indicate some type of valve impact noise, and a careful check of the cams revealed a fairly large deviation of the exhaust cam profile for 2-Cl. This deviation would change the valve velocity and acceleration and could cause excessive noise from valve seat impact or lifter impact. However, even with all of the faults of the 2-Cl, the 2-Cl still tested 1.7 decibels quieter at 3600 rpm than the standard metal assembly.
The present invention thus provides a camshaft assembly for engine use which has numerous advantages with ~uiet operation and low manufacturing costs being two of the most desirable advantages.
Various modes of carrying out the invention are contemplated as being within the scope of the fvllowing claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.
B
.. . .
Claims (24)
1. A method of molding an internal combustion engine camshaft assembly including a camshaft and an integral cam lobe and with said lobe having a crowned cam profile with an apex, comprising the steps of:
(a) providing a mold including a die component axially closeable to define a mold cavity having first surface portions in the shape of a camshaft which defines an axis of rotation and having second surface portions shaped to define the cam lobe of the assembly, said second surface portions including a radially outer surface delineating the crowned cam profile and apex of the cam lobe, said apex of said radially outer surface being disposed radially outwardly of a lower edge of a portion of said die component;
(b) filling said mold cavity with a shrinkable fluid plastics material so that said material forms a camshaft assembly conforming to the shape of and initially engaging said first and second surface portions of said mold cavity;
(c) delaying for a predetermined period of time so that said plastics material hardens and shrinks radially inwardly away from said radially outer mold cavity surface until the apex portion of the camshaft assembly cam profile is finally disposed radially inwardly of said lower edge of said die component portion;
(d) and then opening said mold by moving said die component only in an axial direction so that said lower edge of said die component portion passes freely over said apex portion of the camshaft assembly cam profile.
(a) providing a mold including a die component axially closeable to define a mold cavity having first surface portions in the shape of a camshaft which defines an axis of rotation and having second surface portions shaped to define the cam lobe of the assembly, said second surface portions including a radially outer surface delineating the crowned cam profile and apex of the cam lobe, said apex of said radially outer surface being disposed radially outwardly of a lower edge of a portion of said die component;
(b) filling said mold cavity with a shrinkable fluid plastics material so that said material forms a camshaft assembly conforming to the shape of and initially engaging said first and second surface portions of said mold cavity;
(c) delaying for a predetermined period of time so that said plastics material hardens and shrinks radially inwardly away from said radially outer mold cavity surface until the apex portion of the camshaft assembly cam profile is finally disposed radially inwardly of said lower edge of said die component portion;
(d) and then opening said mold by moving said die component only in an axial direction so that said lower edge of said die component portion passes freely over said apex portion of the camshaft assembly cam profile.
2. The method of claim 1 wherein said plastics material is a nylon based material.
3. The method of claim 1 wherein the filling step comprises injecting molten plastics material into the mold cavity.
4. The method of claim 1 wherein the fluid plastics material comprises a heated molten plastics material and the step of delaying comprises cooling the molten material for a period of time between 0 and 30 seconds.
5. The method of claim 1 wherein the fluid plastics material comprises a heated molten plastics material and the step of delaying comprises cooling the molten material for a period of time less than 5 seconds.
6. The method of claim 1 wherein said plastics material has a shrinkage rate of at least about 0.000067 inches/second.
7. A camshaft assembly constructed in accordance with the steps of claim 1.
8. A camshaft assembly for an internal combustion engine, comprising:
a camshaft defining an axis of rotation; and a cam lobe mounted on said shaft for rotation therewith, said cam lobe having first and second axial ends and an integral crowned cam profile formed in its peripheral surface which includes a shoulder located between said first and second ends which has a radial dimension equal to or greater than the radial dimension of said first and second ends.
a camshaft defining an axis of rotation; and a cam lobe mounted on said shaft for rotation therewith, said cam lobe having first and second axial ends and an integral crowned cam profile formed in its peripheral surface which includes a shoulder located between said first and second ends which has a radial dimension equal to or greater than the radial dimension of said first and second ends.
9. The camshaft assembly of claim 8 wherein said cam profile includes first and second axially extending tapered surfaces, said first tapered surface extending axially from said first end to said shoulder, and said second tapered surface extending axially from said shoulder to said second end.
10. The camshaft assembly of claim 9 wherein said first and second tapered surfaces extend parallel to one another.
11. The camshaft assembly of claim 8 wherein said shoulder extends a radial distance outwardly of said first end and a radial distance equal to said second end.
12. The camshaft assembly of claim 8 wherein both said camshaft and said cam lobe are composed of a plastics material.
13. The camshaft assembly of claim 12 wherein said camshaft and cam lobe are composed of an integral one-piece molded plastics construction.
14. The camshaft assembly of claim 13 wherein said plastics material is a nylon based material.
15. The camshaft assembly of claim 8 wherein said camshaft is composed of a metallic material and said cam lobe is composed of a plastics material.
16. The camshaft assembly of claim 15 further including a hollow sleeve surrounding said camshaft, said sleeve and cam, lobe being composed of an integral one-piece plastics construction.
17. An integral, one-piece, all-plastics camshaft assembly for an internal combustion engine, comprising:
a hollow camshaft composed of a plastics material defining an axis of rotation and including journal members on opposite ends thereof;
a cam lobe composed of said plastics material integral with said camshaft and disposed axially between said journal members, said cam lobe having first and second axial ends and an integral crowned cam profile formed in its peripheral surface which includes a shoulder located between said first and second ends which has a radial dimension equal to or greater than the radial dimension of said first and second ends; and a cam gear composed of said plastics material integral with said camshaft and disposed axially between one of said journal members and said cam lobe.
a hollow camshaft composed of a plastics material defining an axis of rotation and including journal members on opposite ends thereof;
a cam lobe composed of said plastics material integral with said camshaft and disposed axially between said journal members, said cam lobe having first and second axial ends and an integral crowned cam profile formed in its peripheral surface which includes a shoulder located between said first and second ends which has a radial dimension equal to or greater than the radial dimension of said first and second ends; and a cam gear composed of said plastics material integral with said camshaft and disposed axially between one of said journal members and said cam lobe.
18. The camshaft assembly of claim 17 wherein said cam profile includes a first and second axially extending tapered surfaces, said first tapered surface extending axially from said first end to said shoulder, and said second tapered surface extending axially from said shoulder to said second end.
19. The camshaft assembly of claim 18 wherein said first and second tapered surfaces extend parallel to one another.
20. The camshaft assembly of claim 17 wherein said shoulder extends a radial distance outwardly of said first end and a radial distance equal to said second end.
21. The camshaft assembly of claim 17 wherein said plastics material is a nylon-based material.
22. The camshaft assembly of claim 17 wherein said cam gear includes a plurality of axially extending, radially projecting teeth disposed circumferentially about its periphery, said teeth being tapered along their axial length so that their radially outer diameter at one side of said gear is less than the radially outer diameter at the other side of said gear.
23. The camshaft assembly of claim 17 further including a tubular metallic support member disposed within said camshaft.
24. The camshaft assembly of claim 17 further including a solid metallic support member disposed within said camshaft.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US16814288A | 1988-03-14 | 1988-03-14 | |
| US168,142 | 1993-12-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1322284C true CA1322284C (en) | 1993-09-21 |
Family
ID=22610302
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000592532A Expired - Fee Related CA1322284C (en) | 1988-03-14 | 1989-03-02 | Molded camshaft assembly |
Country Status (4)
| Country | Link |
|---|---|
| US (2) | US5320795A (en) |
| JP (1) | JPH01281906A (en) |
| CA (1) | CA1322284C (en) |
| IT (1) | IT1231872B (en) |
Families Citing this family (40)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2150604A1 (en) * | 1994-06-02 | 1995-12-03 | Ralph W. Welsh | Injection molding apparatus, method and product |
| JP3354314B2 (en) * | 1994-09-30 | 2002-12-09 | 本田技研工業株式会社 | Engine camshaft support structure |
| CA2148966C (en) * | 1995-02-09 | 1997-03-04 | Werner Scheliga | Seamless molded skirt and process |
| US5755194A (en) * | 1995-07-06 | 1998-05-26 | Tecumseh Products Company | Overhead cam engine with dry sump lubrication system |
| US6223713B1 (en) | 1996-07-01 | 2001-05-01 | Tecumseh Products Company | Overhead cam engine with cast-in valve seats |
| US5797180A (en) * | 1996-08-28 | 1998-08-25 | Tecumseh Products Company | Method of manufacturing a plastic camshaft with a tubular metal insert |
| US6182631B1 (en) * | 1997-07-07 | 2001-02-06 | Sanshin Kogyo Kabushiki Kaisha | Camshaft for engine |
| US5947070A (en) * | 1997-07-10 | 1999-09-07 | Tecumseh Products Company | Molded plastic camshaft with seal ring |
| DE19738612A1 (en) * | 1997-09-04 | 1999-03-11 | Volkswagen Ag | Camshaft for internal-combustion engine |
| US5829131A (en) * | 1997-11-21 | 1998-11-03 | Chrysler Corporation | Method of making camshaft lobes |
| GB2338912A (en) * | 1998-06-30 | 2000-01-12 | Cummins Engine Co Ltd | Method of manufacturing a camshaft |
| DE10112240A1 (en) * | 2001-03-05 | 2003-01-30 | Ego Elektro Geraetebau Gmbh | Control roller for an electromechanical switching device |
| JP4078051B2 (en) * | 2001-08-29 | 2008-04-23 | 本田技研工業株式会社 | Combined body of driven rotary member for valve and cam |
| US6742491B1 (en) | 2002-12-17 | 2004-06-01 | Tecumseh Products Company | Engine lubrication system |
| ITTO20030314A1 (en) * | 2003-04-23 | 2004-10-24 | Dayco Europe Srl | PULLEY FOR A CONTINUOUSLY VARIED TRANSMISSION RATIO. |
| US7234428B2 (en) * | 2005-07-28 | 2007-06-26 | Briggs And Stratton Corporation | Cam shaft assembly for an engine |
| US9038586B2 (en) * | 2010-03-19 | 2015-05-26 | Eaton Corporation | Rocker assembly having improved durability |
| US9228454B2 (en) | 2010-03-19 | 2016-01-05 | Eaton Coporation | Systems, methods and devices for rocker arm position sensing |
| US8915225B2 (en) | 2010-03-19 | 2014-12-23 | Eaton Corporation | Rocker arm assembly and components therefor |
| US9284859B2 (en) | 2010-03-19 | 2016-03-15 | Eaton Corporation | Systems, methods, and devices for valve stem position sensing |
| US9938865B2 (en) | 2008-07-22 | 2018-04-10 | Eaton Corporation | Development of a switching roller finger follower for cylinder deactivation in internal combustion engines |
| US9581058B2 (en) | 2010-08-13 | 2017-02-28 | Eaton Corporation | Development of a switching roller finger follower for cylinder deactivation in internal combustion engines |
| US10415439B2 (en) | 2008-07-22 | 2019-09-17 | Eaton Intelligent Power Limited | Development of a switching roller finger follower for cylinder deactivation in internal combustion engines |
| US9708942B2 (en) | 2010-03-19 | 2017-07-18 | Eaton Corporation | Rocker arm assembly and components therefor |
| US9291075B2 (en) | 2008-07-22 | 2016-03-22 | Eaton Corporation | System to diagnose variable valve actuation malfunctions by monitoring fluid pressure in a control gallery |
| US20190309663A9 (en) | 2008-07-22 | 2019-10-10 | Eaton Corporation | Development of a switching roller finger follower for cylinder deactivation in internal combustion engines |
| US9016252B2 (en) | 2008-07-22 | 2015-04-28 | Eaton Corporation | System to diagnose variable valve actuation malfunctions by monitoring fluid pressure in a hydraulic lash adjuster gallery |
| US11181013B2 (en) | 2009-07-22 | 2021-11-23 | Eaton Intelligent Power Limited | Cylinder head arrangement for variable valve actuation rocker arm assemblies |
| US9194261B2 (en) | 2011-03-18 | 2015-11-24 | Eaton Corporation | Custom VVA rocker arms for left hand and right hand orientations |
| US10087790B2 (en) | 2009-07-22 | 2018-10-02 | Eaton Corporation | Cylinder head arrangement for variable valve actuation rocker arm assemblies |
| US9885258B2 (en) | 2010-03-19 | 2018-02-06 | Eaton Corporation | Latch interface for a valve actuating device |
| US9874122B2 (en) | 2010-03-19 | 2018-01-23 | Eaton Corporation | Rocker assembly having improved durability |
| JP5812724B2 (en) * | 2011-07-04 | 2015-11-17 | キヤノン株式会社 | Manufacturing method of resin molded gear by injection molding |
| DE102012222752A1 (en) | 2012-12-11 | 2014-06-12 | Mahle International Gmbh | bearing arrangement |
| USD750670S1 (en) | 2013-02-22 | 2016-03-01 | Eaton Corporation | Rocker arm |
| DE112015000034T5 (en) | 2014-03-03 | 2015-11-19 | Eaton Corporation | Valve operating device and method for its production |
| US10279126B2 (en) | 2014-10-07 | 2019-05-07 | Medtronic Minimed, Inc. | Fluid conduit assembly with gas trapping filter in the fluid flow path |
| US10184510B2 (en) * | 2015-05-09 | 2019-01-22 | James Walter Linck | Method of making a carbon composite piston engine crankshaft |
| CN108150372A (en) * | 2016-12-05 | 2018-06-12 | 江苏汉力士液压制造有限公司 | Axial plunger duplex pump helical teeth transmission shaft |
| CN112049703A (en) * | 2020-09-16 | 2020-12-08 | 玉环捷宇机械制造股份有限公司 | Half-iron half-nylon camshaft and manufacturing process thereof |
Family Cites Families (26)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE529071C (en) * | 1930-12-20 | 1931-07-08 | Demag Akt Ges | Control thumb for conveyor machines |
| US2884661A (en) * | 1953-02-27 | 1959-05-05 | Curtiss Wright Corp | Method and apparatus for crankshaft construction |
| US3911761A (en) * | 1974-09-30 | 1975-10-14 | Burroughs Corp | Function lock detent stabilizer |
| AR207088A1 (en) * | 1975-07-29 | 1976-09-09 | Anger Anton Maschbau | PROCEDURE TO PRODUCE AN ARTICLE OF SYNTHETIC MATERIAL |
| US4097702A (en) * | 1977-06-27 | 1978-06-27 | General Motors Corporation | Cam actuated switch |
| US4201360A (en) * | 1978-01-27 | 1980-05-06 | Packer Plastics, Inc. | Injection molding of embossed articles |
| JPS5578114A (en) * | 1978-12-06 | 1980-06-12 | Nissan Motor Co Ltd | Cam shaft for internal combustion engine |
| US4521367A (en) * | 1981-11-16 | 1985-06-04 | Underwood J Larry | Mold, process of molding, and article molded by such process |
| US4453507A (en) * | 1981-11-25 | 1984-06-12 | Briggs & Stratton Corporation | Centrifugally responsive compression release mechanism |
| US4414171A (en) * | 1982-01-28 | 1983-11-08 | The Boeing Co. | Method of making an injection molded propeller |
| US4630498A (en) * | 1982-07-30 | 1986-12-23 | Briggs & Stratton Corp. | Laminated wheel assembly |
| US4655984A (en) * | 1984-10-15 | 1987-04-07 | Champion Spark Plug Company | Method of and apparatus for isostatically pressing a body from particulate material |
| US4741088A (en) * | 1985-03-21 | 1988-05-03 | Somova S.P.A. | Method of making a delivery head for containers of substances to be nebulized having a break-up plastic insert integrally formed with the head |
| US4777004A (en) * | 1985-10-09 | 1988-10-11 | Galer Herbert W | Apparatus and method for molding plastic paint cans |
| JPS62203913A (en) * | 1986-02-28 | 1987-09-08 | Fuji Heavy Ind Ltd | Tappet valve device for automobile engine |
| US4731014A (en) * | 1986-03-12 | 1988-03-15 | Holdt J W Von | Rear opening mold |
| GB8620416D0 (en) * | 1986-08-22 | 1986-10-01 | Stidworthy F M | Differential camshafts |
| US4709757A (en) * | 1986-11-24 | 1987-12-01 | Johnson Service Company | Method of injection molding and plastic part formed thereby |
| DE3705114A1 (en) * | 1987-02-18 | 1988-09-22 | Audi Ag | CAST IRON CAMSHAFT FOR INTERNAL COMBUSTION ENGINES |
| US4755109A (en) * | 1987-04-03 | 1988-07-05 | Fisher Scientific Company Inc. | Snap-together peristaltic mechanism |
| US5041253A (en) * | 1987-10-01 | 1991-08-20 | Husted Royce Hill | Method of making a plastic stabilized composite camshaft |
| DE3913104C1 (en) * | 1989-04-21 | 1990-06-28 | Daimler-Benz Aktiengesellschaft, 7000 Stuttgart, De | |
| IT1238321B (en) * | 1990-01-19 | 1993-07-12 | Bremas Spa | MODULAR CAMSHAFT WITH REMOVABLE CAMS IN PARTICULAR FOR ELECTRIC OR SIMILAR SWITCHES AND SWITCHES |
| US5253546A (en) * | 1990-05-29 | 1993-10-19 | Clemson University | Variable valve actuating apparatus |
| US5243869A (en) * | 1992-05-22 | 1993-09-14 | Emerson Electric Co. | Cam operated indexing drive |
| US5287840A (en) * | 1992-07-30 | 1994-02-22 | General Electric Canada Inc. | Cam sections for a "V"-type diesel engine |
-
1989
- 1989-03-02 CA CA000592532A patent/CA1322284C/en not_active Expired - Fee Related
- 1989-03-09 JP JP1055286A patent/JPH01281906A/en active Pending
- 1989-03-13 IT IT8967177A patent/IT1231872B/en active
- 1989-12-04 US US07/444,839 patent/US5320795A/en not_active Expired - Lifetime
-
1994
- 1994-06-09 US US08/255,665 patent/US5497679A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| IT1231872B (en) | 1992-01-14 |
| US5320795A (en) | 1994-06-14 |
| IT8967177A0 (en) | 1989-03-13 |
| US5497679A (en) | 1996-03-12 |
| JPH01281906A (en) | 1989-11-13 |
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